Relation of Temperature to Susceptibility of Host to Disease.

Abstract

In a previous paper 1 experiments were reported indicating that insolation or immersion in water for short intervals lowers the resistance of guinea pigs to a trypanosome infection. Since the insolation produced a rise of 1.5° C., and, immersion a fall of 2.5° C. in body temperature, there was a possibility that the effect might be referable to temperature changes. Experiments were therefore undertaken to ascertain the effect of low and high environmental temperatures on the relative susceptibility of animals to infection.

In the present series of experiments white rats were used instead of guinea pigs. Rats of the same age and weight were injected intraperitoneally with the same dose of trypanosomes (Tr. evansi) and divided into two groups. One set was placed in a dark room maintained at a temperature of 28° to 30° C., and a relative humidity of 45, the other was placed in a similar room and kept at a temperature of 10° to 12° C. and relative humidity of 70 to 80. In some experiments the rats were kept at the respective temperatures throughout the duration of the test; in others, groups of rats were transferred at short intervals from the hot room to the cold room and vice versa.

Rats were considered preferable to guinea pigs for this type of experiment. In guinea pigs the disease is chronic in character, and the duration of the illness is 3 to 4 months; the criteria for differences in reaction to the virus are, therefore, the incublation period and the intensity of the infection. In rats the disease is acute and of short duration. The duration of illness can be used as a gauge of the effect of various factors on host susceptibility.